Alternative Fuels

Alternative marine fuels: Regulatory mapping

Introduction

This exercise has been conducted by the members of the Alternative Fuels workstream of the Global Industry Alliance to Support Low Carbon Shipping (Low Carbon GIA), with significant inputs and contribution from Mr. Sunil Krishnakumar, ICS, and the IMO Marine Environment and Maritime Safety Divisions.

Disclaimer

Users should be aware that references to IMO instruments may become out of date by the adoption of more recent instruments. Users are therefore invited to consult their national maritime administration or the IMO website for information on the status of referenced instruments.

This work does not prejudge any future policy developments at IMO and does not constitute IMO’s or the Low Carbon GIA’s views on the development of future regulations with respect to alternative maritime fuels.

IMO or the members of the GIA shall not be liable to any person or organization for any loss, damage, or expense caused by reliance on this information.

This mapping was last updated as of 24 November 2025.

This page sets out the outcome of a regulatory mapping exercise with respect to the use of alternative marine fuels and energy converters carried out by the IMO GreenVoyage2050 Global Industry Alliance to Support Low Carbon Shipping (Low Carbon GIA).

This regulatory mapping exercise has identified that while work has been undertaken to develop safety guidelines for the use of methanol and ethanol as fuels, there are currently gaps in safety requirements for low flashpoint and toxic fuels. Work is ongoing at the IMO to address ammonia, hydrogen and low flashpoint diesel. The risk of spills needs to be considered for alternative fuels which are currently not covered by MARPOL Annexes I or II. Certification of methane (CH4) and nitrous oxides (N2O) emissions from engines may be needed for future regulations but are not covered under the current MARPOL Annex VI and NOX Technical Code. With respect to marine fuel quality, there are currently only a few marine fuel quality standards for alternative fuels. However, there may not be a need for such standards specific for marine application, if available standards for land-based fuel can be used.

The regulatory mapping exercise also highlights some observations regarding the definition of fuel oil in the various regulatory documents.

This work is intended to inform and support IMO member States and the wider maritime sector in identifying and addressing potential regulatory challenges that might be faced in the use of a particular alternative fuel option.

This work has been carried out with a specific focus on the safety and environmental aspects of the following fuels and energy sources.

  • Conventional fuels (Diesel/Gas Oil/Fuel Oil)
  • Bio/synthetic liquid diesel fuels
  • Methanol
  • Ethanol
  • Dimethyl Ether (DME)
  • Propane/butane (LPG)
  • Methane (LNG)
  • Ethane
  • Ammonia
  • Hydrogen

It is important to note that considerations such as technology readiness levels, sustainability criteria, impact on short term GHG reduction measures like CII/EEXI and lifecycle GHG analysis of alternative fuels are not covered in this report. Considerations related to the training and employment of crew operating both conventional and alternatively powered ships are also not part of this work.

The results from the regulatory scoping exercise have been presented in a tabular format where the current regulatory readiness levels have been categorized as Low, Medium, and High as per the following criteria agreed by the Low Carbon GIA:

Low: Indicates the absence of related marine standards, regulations and/or interim/final guidelines with required work yet to start

Medium: Indicates the availability of work in progress or approved (waiting for adoption) related marine standards, regulations and/or approved interim/final guidelines

High: Indicates the availability of related marine standards, adopted regulations and/or adopted interim/final guidelines

It should be noted that the identification of a low regulatory readiness level for a particular fuel does not necessarily indicate a potential barrier for the uptake of the fuel, but simply identifies scope for future work to be done by IMO and other stakeholders as appropriate.

Regulatory mapping

Fuel
External standards
IMO SAFETY - SOLAS
IMO ENVIRONMENT - MARPOL
Conventional fuels (Diesel/Gas Oil/Fuel Oil)
Marine standards available

ISO 8217:2024
“”Products from petroleum, synthetic and renewable sources – Fuels (class F) – Specifications of marine fuels”

ISO PAS 23263:2019
“Considerations for fuel suppliers and users regarding marine fuel quality in view of the implementation of maximum 0.50 % sulphur in 2020”

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulate the use of oil fuels with flashpoint > 60°C on board vessels

Medium regulatory readiness level

SOLAS Chapter II regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not include detailed requirements for low-flashpoint fuel oil. Draft interim guidelines for the use of oil fuels with a flashpoint between 52°C and 60°C are currently under development.

High regulatory readiness level

MARPOL Annex I regulates spills and discharges

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2, NOx, and SOx

Bio/synthetic liquid diesel fuels
Marine standards available

ISO8217:2024

“Products from petroleum, synthetic and renewable sources – Fuels (class F) – Specifications of marine fuels”

Includes new references to fuels composed of:

  • synthetic hydrocarbons, renewable hydrocarbons, or hydrocarbons from recycled sources, with molecular structures that are indistinguishable from petroleum hydrocarbons;
  • fatty acid methyl ester (FAME), where permitted as specified in this document;
  • blends of any of the above, where permitted as specified in this document.
Marine standards available

EN 14214:2012+A2:2019

“Liquid petroleum products – Fatty acid methyl esters (FAME) for use in diesel engines and heating applications – Requirements and test methods”

EN 15940:2023

“Automotive fuels – Paraffinic diesel fuel from synthesis or hydrotreatment – Requirements and test methods”

Both EN 14214:2012 and EN 15940:2023 are road transport standards, which have also been used in the marine industry

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulate the use of oil fuels with flashpoint > 60°C on board vessels

Medium regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not include detailed requirements for low-flashpoint fuel oil. Draft interim guidelines for the use of oil fuels with a flashpoint between 52°C and 60°C are currently under development.

High regulatory readiness level

MARPOL Annex I regulates spills and discharges

MARPOL Annex I definition of “oil” covers petroleum in any form, IMO Working Group on the Evaluation of Safety and Pollution Hazards of Chemicals (ESPH) agreed to recommend that energy rich fuels which are not petroleum-based should be covered by Annex I (i.e., not necessary to require biofuels to be carried only on chemical carriers)

Medium regulatory readiness level

MARPOL Annex VI regulates emissions of CO2, NOx and SOx

A Unified Interpretation (MEPC.1/Circ.795/Rev.9) states that a fuel oil blend containing less than or equal to 30% of biofuel or synthetic fuel falls under the definition of marine fuel oil derived from petroleum refining (Regulation 18.3.1) and no further NOx testing is required. In addition, fuel oil blends containing above 30% of biofuel or synthetic fuel can be used when the engine can be operated without changes to its NOx critical components or settings/operating values outside those as given by that engine’s approved Technical File.

Methyl Alcohol (Methanol)
Marine standards in progress

 ISO6583:2024

“Methanol as a fuel for marine applications – General requirements and specifications

Currently, IMPCA[1] Methanol reference specification and ASTM[2] D1152 standard are used when specifying methanol quality.

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not cover include detailed requirements for as fuel, but it is included in MSC.1/Circ.1621 Interim guidelines for the safety of ships using methyl/ethyl alcohol as fuel.

IMO will initiate work on including these in its mandatory instruments.

Low regulatory readiness level

Methanol is assigned category Y as per the IBC Code, meaning it presents a hazard to either marine resources or human health. MARPOL Annex II requirements do not apply to spills and discharges of methanol as fuel.

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Ethyl Alcohol (Ethanol)
No marine standards available

No standard as a marine fuel

ISO has initiated work on this standard.

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not cover include detailed requirements for as fuel, but it is covered by MSC.1/Circ.1621 Interim guidelines for the safety of ships using methyl/ethyl alcohol as fuel.

 

Low regulatory readiness level

Ethanol is assigned category Y as per the IBC Code, meaning it presents a hazard to either marine resources or human health. MARPOL Annex II requirements do not apply to spills and discharges of ethanol as fuel.

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Dimethyl Ether (DME)
No marine standards available

No standard as a marine fuel

Low regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

No specific requirements or guidelines are available for dimethyl ether (DME) as a fuel.

Low regulatory readiness level

For gas carriers (IGC Code), the use of DME cargo as a fuel is subject to acceptance by the Administration, provided that the same level of safety as natural gas (methane) is ensured (Resolution MSC.566(109)), which enters into force on 1 July 2026).

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Propane/butane (LPG)
No marine standards available

No standard as a marine fuel

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not include detailed requirements for LPG as fuel, but it is covered in MSC.1/Circ.1666 Interim guidelines for the safety of ships using LPG fuels were approved by MSC 107 in June 2023.

High regulatory readiness level

For gas carriers (IGC Code) using LPG cargo as fuel, MSC.1/Circ.1679 Interim guidelines for use of liquefied petroleum gas (LPG) cargo as fuel have been approved by MSC 108 in June 2024. Draft mandatory requirements are to be approved at MSC 111.

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Low regulatory readiness level

Fugitive emissions of propane or butane are not currently regulated under MARPOL Annex VI.

Methane (LNG)
Marine standards available

ISO 23306:2020
“Specification of liquefied natural gas as a fuel for marine applications”

High regulatory readiness level

SOLAS Chapter II-1 and II-2 regulate methane (LNG) as fuel through SOLAS Ch II-1 Part G (low-flashpoint liquid fuel or gas) and the IGF Code.

High regulatory readiness level

For gas carriers (IGC Code) using LNG cargo as fuel, IGC Code Chapter 16 applies.

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Low regulatory readiness level

Fugitive emissions of methane are not currently regulated under MARPOL Annex VI.

Ethane
No marine standards available

No marine standards available

Low regulatory readiness level

SOLAS Chapter II regulates low-flashpoint fuels (< 60°C) or gas through

No specific requirements or guidelines available for ethane as fuel.

Medium regulatory readiness level

For gas carriers (IGC Code) using Ethane cargo as fuel, draft mandatory requirements are to be approved at MSC 111.

High regulatory readiness level

MARPOL Annex VI regulates emissions of CO2 and NOx

Low regulatory readiness level

Fugitive emissions of ethane are not currently regulated under MARPOL Annex VI.

Ammonia
No marine standards available

No marine standards available

High regulatory readiness level

SOLAS Chapter II regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not include detailed requirements for ammonia as fuel, but it is covered in MSC.1/Circ.1687 Interim guidelines for the safety of ships using ammonia as fuel were approved by MSC 108 in December 2024.

 

High regulatory readiness level

For gas carriers (IGC Code), the use of ammonia cargo as a fuel is subject to acceptance by the Administration, provided that the same level of safety as natural gas (methane) is ensured (Resolution MSC.566(109)), which entered into force on 1 July 2026).

Draft interim guidelines for the use of ammonia cargo as fuel are currently under development.

Low regulatory readiness level

“Ammonia aqueous” is assigned category Y as per the IBC Code, meaning it presents a hazard to either marine resources or human health. MARPOL Annex II requirements do not apply to spills and discharges of ammonia as fuel. It should also be noted that it is expected that the fuel will be anhydrous ammonia rather than aqueous ammonia.

MEPC has agreed on a work item to develop guidelines for the management of ammonia effluents.

Medium regulatory readiness level

MARPOL Annex VI regulates emissions of NOx

The NOx Technical Code will be updated to apply for non-carbon-containing fuels and mixtures

Low regulatory readiness level

N2O, emissions are not currently regulated under MARPOL Annex VI.

Low regulatory readiness level

Fugitive emissions of ammonia are not currently regulated under MARPOL Annex VI.

Hydrogen
No marine standards available

No standard as a marine fuel

 ISO 14687:2019

“Hydrogen fuel quality – Product specification”

Medium regulatory readiness level

SOLAS Chapter II-1 and II-2 regulates low-flashpoint fuels (< 60°C) or gas through

The IGF Code does not include detailed requirements for hydrogen as fuel. Draft interim guidelines for the safety of ships using hydrogen as fuel are finalized and expected to be adopted by MSC 111 in 2026.

Medium regulatory readiness level

For gas carriers (IGC Code), resolution MSC.565(108) adopted by MSC 108 in December 2024 provides interim recommendations for the carriage of liquid hydrogen in bulk alongside the IGC code.

Medium regulatory readiness level

MARPOL Annex VI regulates emissions of NOx

The NOx Technical Code will be updated to apply for non-carbon-containing fuels and mixtures.

Low regulatory readiness level

Fugitive emissions of hydrogen are not currently regulated under MARPOL Annex VI.

1 International Methanol Producers and Consumers Association

2 ASTM standards are developed, published, and maintained by ASTM International, a standards organization formerly known as the American Society for Testing and Materials

Main IMO conventions/instruments considered

SOLAS

SOLAS

The International Convention for the Safety of Life at Sea (SOLAS), 1974 specifies minimum standards for the construction, equipment, and operation of ships, compatible with their safety. The current SOLAS Convention includes Articles setting out general obligations, amendment procedure, and so on, followed by an Annex divided into 15 Chapters.

Relevant sections of the SOLAS Convention and related codes are:

SOLAS Chapter II-1
Construction – Structure, subdivision and stability, machinery and electrical installations

SOLAS Chapter II-2
Construction – Fire protection, fire detection and fire extinction

IGF Code

IGF Code

The International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code) contains mandatory provisions for the arrangement, installation, control and monitoring of machinery, equipment, and systems using low-flashpoint fuels, currently focused on liquefied natural gas (LNG).

IGC Code

IGC Code

The International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) provides design and construction standards for all ships engaged in the carriage of liquefied gases having a vapour pressure exceeding 2.8 bar absolute at a temperature of 37.8°C, and certain other substances listed in chapter 19 of the Code

IBC Code

IBC Code

International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code) provides an international standard for the safe carriage in bulk by sea of dangerous chemicals and noxious liquid substances listed in chapter 17 of the Code.

MARPOL

MARPOL

The International Convention for the Prevention of Pollution from Ships (MARPOL), 1973, as modified by the Protocol of 1978 (as amended), is the main international convention covering the prevention of pollution of the marine environment by ships from operational or accidental causes. The convention currently includes six technical Annexes.

Relevant sections of the MARPOL Convention and related codes are:

MARPOL Annex I
Regulations for the prevention of pollution by oil

MARPOL Annex II
Regulations for the control of pollution by noxious liquid substances in bulk

MARPOL Annex VI
Regulations for the prevention of air pollution from ships

NOx Technical Code 2008: The Technical Code on control of emission of nitrogen oxides from marine diesel engines (NTC 2008) specifies requirements for the testing, survey and certification of marine diesel engines to ensure they comply with the nitrogen oxides emission limits of regulation 13 of MARPOL Annex VI.

Review of existing references to and definitions of fuels in IMO conventions/instruments

1. References to low-flashpoint fuels in SOLAS 1974 and related codes

Observation: As per SOLAS regulation II-2/4.2.1.1 ships are not allowed to use oil fuel with a flashpoint of less than 60°C – with the exception for emergency generators not less than 43°C and other cases with specific provisions.

SOLAS regulations II-1/56 and II-1/57 apply to ships using low-flashpoint fuels and refers to the IGF Code. Paragraph 2.2.10 of the IGF Code stipulates that oil fuels may include distillate and residual fuels.

While the term low-flashpoint fuel is defined in SOLAS regulation II-1/2.29 and paragraph 2.2.28 of the IGF Code, the term oil fuel is not defined in SOLAS Chapter II-1 or SOLAS Chapter II-2 or the IGF Code.

SOLAS Chapter II-1 Part A – General
Regulation II-1/2 Definitions

.29 Low-flashpoint fuel means gaseous or liquid fuel having a flashpoint lower than otherwise permitted under regulation II-2/4.2.1.1

SOLAS Chapter II-1 Part G – Ships using Low-Flashpoint Fuels
Regulation II-1/56 Application
Regulation II-1/ 57 Requirements for Ships Using Low-Flashpoint Fuels

SOLAS Chapter II-2 Part B – Prevention of Fire and Explosion
Regulation II-2/4 Probability of ignition

.2.1 Limitations in the use of oils as fuel:

The following limitations shall apply to the use of oil as fuel:

.1 except as otherwise permitted by this paragraph, no oil fuel with a flashpoint of less than 60°C shall be used; *

*Refer to Recommended procedures to prevent the illegal or accidental use of low flashpoint cargo oil as fuel (resolution A.565(14))

IGF Code Part A
2.2 Definitions

2.2.10Dual fuel engines means engines that employ fuel covered by this Code (with pilot fuel) and oil fuel. Oil fuels may include distillate and residual fuels.

2.2.28 Low-flashpoint fuel means gaseous or liquid fuel having a flashpoint lower than otherwise permitted under paragraph 2.1.1 of SOLAS regulation II-2/4.

2. References to fuel supply for machinery in SOLAS 1974 and related codes

Observation: SOLAS regulation II-1/26.3.4 refers to fuel oil supply systems for boilers or engines and MSC/Circ.851 contains guidelines on engine-room oil fuel systems. SOLAS regulation II-1/26.11 stipulates requirements for the location and arrangement of vent pipes for fuel oil settling and service tanks, and the number and capacity of fuel oil service tanks.

In addition to the limitations in the use of oils as fuel with respect to flashpoint, SOLAS regulation II 2/4.2 lists regulations regarding the arrangements for oil fuel, lubricating oil and other flammable oils. SOLAS regulation II-2/4 also makes reference to MSC.1/Circ.1321 Guidelines for measures to prevent fires in engine-rooms and cargo pump-rooms, which includes conventional oil fuels e.g. Heavy oil fuel, intermediate oil fuel (380 and 180) etc. under the definition of flammable oils.

Neither of the terms fuel oil nor oil fuel is defined in SOLAS.

SOLAS Chapter II-1 Part C – Machinery Installations
Regulation II-1/26 General

.3 Means shall be provided whereby normal operation of propulsion machinery can be sustained or restored even though one of the essential auxiliaries becomes inoperative. Special consideration shall be given to the malfunctioning of

.4 the fuel oil supply systems for boilers or engines**

**Refer to Guidelines to minimize leakage from flammable liquid systems (MSC/Circ.647) and Guidelines on engine-room oil fuel systems (MSC/Circ.851).

.11 Location and arrangement of vent pipes for fuel oil service, settling and lubrication oil tanks shall be such that in the event of a broken vent pipe this shall not directly lead to the risk of ingress of seawater splashes or rainwater. Two fuel oil service tanks for each type of fuel used on board necessary for propulsion and vital systems or equivalent arrangements shall be provided on each new ship, with a capacity of at least 8 h at maximum continuous rating of the propulsion plant and normal operating load at sea of the generator plant. ***

*** Refer to regulation II-2/4.2, Arrangements for oil fuel, lubrication oil and other flammable oils.

SOLAS Chapter II-2 Part B – Prevention of Fire and Explosion*
Regulation II-2/4 Probability of ignition

*Refer to Guidelines for measures to prevent fires in engine-rooms and cargo pump-rooms (MSC.1/Circ.1321)

MSC.1/Circ.1321 Guidelines for measures to prevent fires in engine-rooms and cargo pump-rooms
Section 3 Definitions

3.7Flammable oils, for the purpose of these Guidelines, means oils used in machinery spaces as those listed in table 1.

3. Definitions of fuel in MARPOL Annex I – Regulations for the Prevention of Pollution by Oil

Observation: The term oil fuel is defined in MARPOL Annex I regulations 1.4 and 12A.3.1. While the term fuel oil is mentioned as a type of oil, no specific definition of the term is provided. MSC-MEPC.2/Circ.17 and MEPC.1/Circ.879 provide definitions for biofuels and energy-rich fuels respectively.

MARPOL Annex I Regulations for the Prevention of Pollution by Oil
Regulation 1 Definitions

.1 Oilmeans petroleum in any form including crude oil, fuel oil, sludge, oil refuse and refined products (other than those petrochemicals which are subject to the provisions of Annex II of the present Convention) and, without limiting the generality of the foregoing, includes the substances listed in appendix I to this Annex.

.4 Oil fuel means any oil used as fuel in connection with the propulsion and auxiliary machinery of the ship in which such oil is carried.

MARPOL Annex I Regulations for the Prevention of Pollution by Oil
Regulation 12A Oil fuel tank protection

.3 For the purpose of this regulation, the following definitions shall apply:

.1 “Oil fuel” means any oil used as fuel oil in connection with the propulsion and auxiliary machinery of the ship in which such oil is carried.

MARPOL Annex I Regulations for the Prevention of Pollution by Oil
Appendix 1 List of oils

Oils: Clarified, Crude oil, Mixtures containing crude oil, Diesel oil, Fuel oil no.4, Fuel oil no.5, Fuel oil no.6, Residual fuel oil, Road oil, Transformer oil, Aromatic oil (excluding vegetable oil), Lubricating oils and blending stocks, Mineral oil, Motor oil, Penetrating oil, Spindle oil, Turbine oil

MSC-MEPC.2/Circ.17 2019 Guidelines for the carriage of blends of MARPOL Annex I cargoes and biofuels
Section 3 Definitions

.1 Biofuels are ethyl alcohol, fatty acid methyl esters (FAME) and vegetable oils (triglycerides), as identified in chapters 17 and 18 of the IBC Code or the MEPC.2/Circular.

MEPC.1/Circ.879 Guidelines for the carriage of energy-rich fuels and their blends
Section 3 Definitions

.1 Energy-rich fuels are identified by the PPR Working Group on the Evaluation of Safety and Pollution Hazards of Chemicals (ESPH), based on an appropriate proposal, as products falling under the scope of these Guidelines. Energy-rich fuels will be recorded in annex 12 of the MEPC.2/Circular on Provisional categorization of liquid substances in accordance with MARPOL Annex II and the IBC Code. Energy-rich fuels are wholly or partly derived from non-petroleum feedstock and they can be produced either without blending as such or by blending with petroleum products.

Section 4Description of energy-rich fuels

.1 An energy-rich fuel is obtained from biological origin or non-petroleum sources (e.g. algae, vegetable oils) or is a blend of petroleum-based fuel and a product obtained from biological origin or non-petroleum sources (e.g. algae, Gas-to-Liquid (GTL) process, Hydrotreated Vegetable Oil (HVO), co-processing).

4. Definitions of fuel in MARPOL Annex VI – Regulations for the Prevention of Air Pollution from Ships

Amendments to MARPOL Annex V on low-flashpoint fuels and other fuel oil related issues, adopted through the resolution MEPC.385(81), on 22 March 2024, and entered into force from 1 August 2025.

Observation: The term fuel oil is defined in Regulation 2.1.14 of MARPOL Annex VI. With regards to the definition of low-flashpoint fuel (Regulation 2.1.20), MARPOL Annex VI differs to the SOLAS definition in that the term fuel oil is used instead of fuel. The MARPOL Annex VI definition of fuel oil could be considered more representative as it refers to any fuel when compared to the much more restricted reference to oil used as fuel as defined in MARPOL Annex I.

Regulation 18.3 of MARPOL Annex VI stipulates the specific requirements applicable to fuel oil for combustion purposes delivered to and used on board ships.

MARPOL Annex VI Regulations for the Prevention of Air Pollution from Ships
Regulation 2 Definitions

.1 For the purpose of this Annex:

.14 Fuel oil means any fuel delivered to and intended for use on board a ship.

.20 Low-flashpoint fuel means gaseous or liquid fuel oil having a flashpoint lower than otherwise permitted under paragraph 2.1.1 of regulation 4 of chapter II-2 of the International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended.

.21 Marine diesel engine means any reciprocating internal combustion engine operating on liquid or dual fuel, to which regulation 13 of this Annex applies, including booster/compound systems if applied. In addition, a gas-fuelled engine installed on a ship constructed on or after 1 March 2016 or a gas-fuelled additional or non-identical replacement engine installed on or after that date is also considered as a marine diesel

.33 Gas fuel means a fuel oil with a vapour pressure exceeding 0.28 MPa absolute at a temperature of 37.8°C*

*Refer to paragraph 2.2.18 of the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code).

Regulation 4 Equivalents

.1 The Administration of a Party may allow any fitting, material, appliance or apparatus to be fitted in a ship or other procedures, alternative fuel oils, or compliance methods used as an alternative to those required by this Annex if such fitting, material, appliance or apparatus or other procedures, alternative fuel oils, or compliance methods are at least as effective in terms of emissions reductions as those required by this Annex, including any of the standards set forth in regulations 13 and 14.

Regulation 18 Fuel oil availability and quality

.3 Fuel oil delivered to and used on board ships to which this Annex applies shall meet the following requirements:

.1 except as provided in paragraph 3.2 of this regulation:

.1.1 the fuel oil shall be blends of hydrocarbons derived from petroleum refining. This shall not preclude the incorporation of small amounts of additives intended to improve some aspects of performance;

.1.2 the fuel oil shall be free from inorganic acid; and

.1.3 the fuel oil shall not include any added substance or chemical waste that:

.1 the fuel oil shall not include any added substance or chemical waste that:

.2 is harmful to personnel, or

.3 contributes overall to additional air pollution.

.2 fuel oil derived by methods other than petroleum refining shall not:

.2.1 exceed the applicable sulphur content set forth in regulation 14 of this Annex;

.2.2 cause an engine to exceed the applicable NOx emission limit set forth in paragraphs 3, 4, 5.1.1 and 7.4 of regulation 13;

.2.3 contain inorganic acid; or

.2.4.1 jeopardize the safety of ships or adversely affect the performance of the machinery, or

.2.4.2 be harmful to personnel, or

.2.4.3 contribute overall to additional air pollution